A shawl cardigan will keep you warm on a chilly spring night, or out on a boat. JFK wore his shawl collar cardigan while boating to keep him warm. This pairs well with a linen pant or the shorts mentioned above.
A striped tie is another spring essential, especially when you have to dress up your outfit a bit. Pair this with a plain white button down or an oxford blue shirt. Roll those sleeves or opt for a short sleeve shirt—it is spring after all. Remain cool, but still professional and classic.
Loafers or other dress shoes can be paired with shorts or pants to dress up a style. For the classic look of JFK, go for round toes instead of squared.
Then because we can’t forget accessories and attention to detail: wayfarer sunglasses are perfect for sunny days. But to make it a bit more modern or your own personal flare go for the clubmaster. It’s a similar silhouette but will still add a classic look to break up an outfit to be more casual like the wayfarer did for JFK.